1. Field of the Invention
The present invention relates generally to computer security, and more particularly but not exclusively to methods and apparatus for content filtering.
2. Description of the Background Art
A computer network may employ various content filtering services to protect the network from malicious codes and other computer security threats. Content filtering services may be performed in a gateway computer of a private computer network. The gateway computer serves as a gate keeper between a public computer network and the private computer network. Examples of content filtering services that may be performed at the gateway computer include antivirus, antispam, URL (uniform resource locator) filtering, etc. Traditionally, the gateway computer is deemed the best place to perform all content filtering services because it provides a central location and is generally easy to maintain from the point of view of a network administrator. However, content filtering at a gateway computer is not without its share of drawbacks. Content filtering at the gateway computer is CPU (central processing unit) intensive, taking substantial CPU time from other gateway tasks. The size of patterns used by content filtering systems also grows at a fast rate, making content filtering at the gateway computer difficult if not unsustainable in the future. Furthermore, policy enforcement done at the gateway computer requires additional information (e.g., databases) to be maintained at the gateway computer.